In yesterday’s write-up, I covered the playoff bye dynamic and what historical effects it has had on team performance. Today, I’d like to take a look at another game element that has a measurable effect on games and is also prevalent in this week’s slate of games. That effect is weather. Each of the three games being played outdoors this weekend have a weather element to them, and everyone from bettors to players to analysts to talking heads have chipped in with their thoughts on how each condition will effect each team and game. But as always, I like to slice right through the noise and use a data-driven approach.
Whether Weather Has An Effect
Let’s first take a look at temperature. In a study conducted by advancedfootballstats.com, teams were separated out by four climate types: warm, moderate, cold, and domed. Those teams’ performances as a road team were then analyzed in temperature increments to see the correlation between temperature and win percentage, and below are the results of that analysis. As you can see, the most discernible effect temperature has is on domed teams playing in cold weather. The rest of the results are what I would consider to be inconclusive, given that warm teams had the highest win percentage at extreme lows (11-20 °F) and cold teams had the best win percentage at extreme highs (81-90 °F). That would obviously go against the what you typically hear from just about everyone.
Next up is precipitation, which is obviously split into games with rain and games with snow. The former typically has a negligible effect on games, which may go against common narratives you hear. A fantastic analysis done by Chris Allen from 4for4 showed that when compared to a “clear” game (60-75 °F, <9 mph wind), rain games have just a 2.4% decrease in total pass attempts, a 2.0% decrease in air yards, and a 0.5% decrease in deep pass attempts. Even target distributions by position don’t see a noteworthy enough change, which you can see below. Before tackling snow’s effect, I thought I’d quickly mention that games with significant wind see a negligible 2.4% decrease in total pass attempts and a 0.8% decrease in air yards, but a most-certainly noteworthy 6.2% decrease in deep pass attempts and a 4-8 point decrease in actual game totals when reaching 15 mph.
Snow is a weird weather element when looking at the data. The common narrative with snow is that passing volume decreases and rushing volume increases, which is generally true with a 6% swing in pass / run ratio. But what about the effect on efficiency of those types of plays? In the aforementioned 4for4 analysis, there was an 8.3% drop-off in total pass attempts, yet just a 1.4% decrease is deep pass percentage and a 5.3% increase in air yards. But not all snow is the same. In a study done by Pro Football Focus, it was found that “light” snow has a very negligible effect on passing efficiency (1.8% increase in completion percentage) and rushing efficiency (0.27 more yards per carry). It isn’t until snow is “heavy” that the there begins to be a more profound effect, with a 8.4% dip in completion percentage being the most notable change. I believe that public bettors tend to overreact at just the very sight of snow, and you see this with the light snow expected to be on the field for the Colts-Chiefs game despite the fact that it isn’t expected to snow at all during the actual game.
#5 Chargers (13-4) @ #2 Patriots (11-5)
The Patriots are a team the model can channel their Dennis Green with and say, “They are who we thought they were”. Coming into the season, the Patriots were expected to regress just a tad. They finished the 2017 season as the #3 team according to the model and they were projected to finish the 2018 season sixth-best with 9.66 expected wins. They ended up finishing the 2018 regular season with the fifth-best expected wins total, with 9.86. The Patriots never dipped lower than 9.21 expected wins and peaked at 10.03, showing that their performance has been consistent. Known to draw a lot of public money, their prices are often inflated and overvalued and the model finding zero times throughout the season to back them supports that. As for betting against the Patriots, the model found plenty of opportunities and went 5-2 for +13.36 units and a 45.01% ROI if we ignore the Week 5 model play backing the Colts against the Patriots on Thursday Night Football which remains the only model play I’ve personally advised against backing.
So what reasons would there be to back the Patriots this week against the Chargers? The model doesn’t really find any across the board. The Patriots rank behind the Chargers in every model category except special teams, which accounts for roughly just 6% of total team strength. Granted, the Patriots trail the Chargers in pass offense, rush offense, and pass defense by just a combined nine spots across all three categories, but it’s the Patriots 18th ranked rush defense going up against the Chargers’ sixth-best rush offense that will pose a problem in this game.
If there’s one thing the Patriots do have going for them, it’s that their defensive personnel and typical gameplan fits the mold of what brings down Philip Rivers’ effectiveness. The Patriots certainly have the ability to play man coverage, which yields 1.55 less yards per attempt from Rivers compared to zone coverage. The Patriots also pressure opposing quarterbacks at the fifth-highest rate in the league, which limits Rivers’ ability to wait in the pocket and fire deep to Mike Williams who may be drawing favorable coverage in this matchup if the Patriots’ top corner Stephon Gilmore is tasked with covering Keenan Allen.
Hopefully most of you have been following along on Twitter and received the play as soon as it was made, as I am only seeing LAC +4 available now, which would reduce the points of disagreement to 1.7 and no longer be enough for a model play.
#6 Eagles (10-7) @ #1 Saints (13-3)
The Eagles and Saints are two teams I’ve covered in detail in past newsletters, so I’ll just quickly recap their model numbers. The Eagles stand 15th overall in the model with 8.26 expected wins whereas the Saints sit fourth overall with 10.29 expected wins. An argument can be made that the Saints are actually undervalued in the model, as their adjusted Pythagorean win total for this year is 11.45 and of the remaining playoff teams, only the Colts possess a larger gap between the two numbers. Despite this game featuring the largest spread of the playoffs thus far, there is quite a bit to unpack in this game. Yes the Saints absolutely throttled the Eagles in their regular season matchup, but the Eagles are certainly a much different team this time around and they come into this game with a few things that could work their way.
The Eagles are of course coming off a win against the top-ranked defense of the Chicago bears. In particular, they’ll be able to take what helped beat the top-ranked rush defense in the conference and apply that to the Saints rush defense which trailed the Bears’ unit by one spot. In addition, the Saints defense possesses a weakness against the running back position in the passing game as they have the fourth-worst pass defense DVOA against RBs. That means ex-Saint Darren Sproles may find himself in the mix quite a bit this time around, as he was yet to return from his near season-long injury by the time of the first matchup.
Establishing their running backs as a receiving threat will help keep the Saints defense modest, and should help open up the deep ball which has killed the Saints this season who rank as the worst in the league against passes of 15 yards or more. The problem is that Nick Foles has not always been a great candidate to throw deep. Last week Foles completed just two of his seven attempts at that range, including an interception (although he did have two 14 yard completions, one of which went for a TD). Whether the Eagles will get the Foles who averaged 7.2 and 5.3 yards per attempt in the last two regular seasons or the Foles that averaged 9.2 YPA in the 2017 playoffs will probably determine how successful the Eagles’ passing attack will be come Sunday night.
As for the model, the Saints are made to be three point favorites against the Eagles on a neutral field when coming off a bye. The remaining game-specific factors then bring the spread up to NO -7.1, which is just 0.9 points off the current line of NO -8. That of course means that the Saints would become a model play beginning at -5, whereas the Eagles would become one at +9.5 (but the model removes spreads of +7 or higher from consideration).
That will wrap it up for the Divisional round, but I will see you all next weekend for the conference championships. Don’t forget to follow me on Twitter, where you can catch model plays the second they are made.
1/4: Saturday Wild Card 1/5: Sunday Wild Card 1/11: Saturday Divisional 1/12: Sunday Divisional
- 1/19: Conference Championships
- 2/2: Super Bowl
Thanks again for reading!